The invention relates to a method for regulating the range of the headlights of a vehicle according to the load.
Regulation such as referred to here includes not only a static adjustment of the headlight range corresponding to the load state of the vehicle (cargo in the trunk, number of passengers, etc.), but also to a dynamic form of regulation in which the range is kept constant regardless of the pitching movements of the vehicle.
Pitching of a vehicle around its transverse axis is a function of (among other things) vehicle speed, and at high speed frequently results in the front end of the car moving upward, with a corresponding change of the headlight range due to a corresponding reduction of the tilt of the headlights. Conversely, the tilt of the headlights is smaller at lower speeds since the vehicle then does not align itself or at least does so to a lesser degree. The inclination of the vehicle in the lengthwise direction depends on its geometry and spring characteristics, and can also depend for example on the level of the fuel in the tank and the air pressure in the tires.
In conventional automatic headlight range regulation systems, a sensor of some type determines the height of the vehicle body relative to the front and rear axles for example. From the difference with respect to the required level, it generates a correction signal to adjust the tilt of the headlights in a known manner for the purpose of keeping the headlight range constant. The term "headlight range" refers to the point where the main beam of the headlights strikes the surface of the road. The range is determined for example by using a vertical wall at a distance of about 10 meters in front of the vehicle. The main beam, assuming a headlight range of 50 meters, will drop off by 1/5 to 4/5 of the height of the headlights.
It is also known to compensate for the acceleration-dependent pitching movements of the vehicle that occur during acceleration and result in a corresponding change in the headlight range. All of these methods have in common the goal of achieving a constant headlight range of approximately 50 meters.
The value of 50 meters, however, is sufficient at low speeds. However, at high speeds, it is simply insufficient because in the time required for a driver to react, the vehicle can travel a distance that is several times this value. Conversely, when the vehicle is standing still, a range of 50 meters can be perceived by the driver as being too great.
The object of the present invention is to provide a method of the type recited at the outset which adjusts headlight range to the actual need of the driver.
This object is achieved by the method according to the invention, in which the headlight range is adjusted as a function of vehicle speed. That is, the headlight range is increased at higher speeds, so that the visual field is expanded, while at low speeds, however, the headlight range remains at the usual value of 50 meters as described above. In this manner, it is possible to illuminate the highway even with low beams in such fashion that the requirements of persons driving in traffic are taken into account. Of course blinding of oncoming traffic is also avoided while increasing the headlight range.
The change in headlight range can be continuous or in a more simplified approach, by a stepwise adjustment. A specific vehicle speed is associated with each step, above and below which the headlight range has defined values separated from one another by the step. The number of steps is arbitrary. It is possible for example to work with only one step. However it is equally possible to have a plurality of steps.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.